1. Technical Field of the Invention
The present invention relates to an optical color separation and synthesis system for use in a reflective type projection display apparatus, and a method of constructing an optical color separation and synthesis system.
2. Description of the Related Art
In an optical color separation and synthesis system for use in a projection display apparatus for projecting a color image, white light emitted from a light source unit is separated into light of three primary colors of red (R), green (G), and blue (B), and the three-primary-color light is guided to a corresponding spatial light modulation element of each color. Furthermore, color synthesized light obtained by synthesizing the color of each color light modulated by each color spatial light modulation element according to a video signal is emitted on the side of a projection lens.
As this type of optical color separation and synthesis system, the present applicants have previously proposed an example in which four first to fourth polarization beam splitters are arranged as a plurality of polarization beam splitters in such a manner that polarization separating surfaces of the respective polarization beam splitters form an X-shape as viewed from an upper-surface side. Moreover, if necessary, a wavelength selecting polarization transforming plate is disposed facing any of the first to fourth polarization beam splitters, the first polarization beam splitter is disposed on the side of the light source unit, and the fourth polarization beam splitter is disposed on the side of the projection lens. Then, the spatial light modulation elements of the respective colors corresponding to RGB are disposed facing any surface of the second, third polarization beam splitters (see, e.g., Japanese Patent Application Laid-Open Nos. 2002-228809 and 2002-287094).
In the Japanese Patent Application Laid-Open Nos. 2002-228809 and 2002-287094, although not shown, to construct the optical color separation and synthesis system, all of the four first to fourth polarization beam splitters are integrally bonded beforehand by a light transmitting bonding member (e.g., adhesive). Alternatively, two or three of the four first to fourth polarization beam splitters are integrally bonded beforehand by the light transmitting bonding member (e.g., adhesive). Thereafter, the four first to fourth polarization beam splitters are secured onto a base platform in such a manner that the polarization separating surfaces of the respective polarization beam splitters are arranged in an X-shape as viewed from the upper-surface side.
Additionally, in the Japanese Patent Application Laid-Open Nos. 2002-228809 and 2002-287094, an optical characteristic of the optical color separation and synthesis system is satisfactorily obtained. However, to integrally bond at least two or more polarization beam splitters to each other beforehand by the light transmitting bonding member (e.g., adhesive), the polarization beam splitters are mutually positioned. Moreover, if necessary, the wavelength selecting polarization transforming plate is inserted and integrally bonded between the facing surfaces of the polarization beam splitters. Therefore, much time is required in constructing the optical color separation and synthesis system, and problems occur in productivity.